The invention relates to a seat hinge, and more particularly, to a seat hinge structure for a motor vehicle employing an internal inertia sensitive element which prevents articulation of the hinge in certain conditions.
Passenger cars having two side doors and a rear occupant seating area generally must be provided with a mechanism which permits the front seat back to be rotated forward, thereby provding sufficient clearance for access to the rear seating area, and to permit entrance to and egress from the rear seating area by passengers. In the past, manually operated hinge mechanisms were pervalent. Theses devices required the passenger to manually actuate a lever or other mechanism in order to unlatch the seat back, thereby allowing it to be swung forward. Latching mechanisms are necessary in order to comply with Federal Motor Vehicle Safety Standards (FMVSS) which require that the front seat back be held in a nearly vertical position when the vehicle is subjected to suden declerations, as would be experienced during a frontal impact. The intent of these requirements is to prevent the seat back from striking the front seat occupants in such conditions. In an effort to improve comfort and convenience of motor vehicles, manufacturers have recently provided inertia sensitive seat back hinge mechanisms. These devices empoly an internal inertia sensitive element which, when subjected to high rates of deceleration, causes the seat back to be locked, thereby preventing it from moving forward due to the force of such deceleration. Under normal circumstances, however, the rear seat passenger may simply push the front seat back forward without first actuating a release lever.
An additional customer feature which is being provided in modern motor vehicles in increasing numbers are reclining devices which permit the angle of the front seat back relative to the seat bottom to be changed as desired by the seat occupant.
Many seat back hinge mechanisms having an inertia sensitive latch and a reclining feature have been heretofore proposed and implemented. One such design, which is described by U.S. Pat. No. 4,372,610, issued on Feb. 8, 1983, to A. J. Fisher III, et al, which in assigned to the assignee of the application, empolys a quadrant attached to the lower hinge structure and features an internal arcuate aperture through which a pin afixed to the upper hinge structure passes as the seat back is moved between normal and forward positions. The quadrant according to the previously mentioned patent, however, presents a protruding edge surface toward the rear seat area when the seat back is rotated forward. This edge surface is objectionable in that rear seat occupants could contact it while entering or egressing the rear seat area. This edge surface also prevents the application of interior trim fabrics over this area due to the potential for wearing or tearing of the trim.
During use, motor vehicle seats are subjected to significant force loadings exerted by the weight of the occupants during cornering manevers and due to vehicle vibrations. These loadings and others acting on the seat, such as those imposed when occupants grasp or push the seats while entering or egressing the vehicle, may cause mislignment between the seat back and bottom to occur. Moreover, precise alignment between these structures cannot be guaranteed during the production process due to ordinary component fabrication and assembly tolerance variations. Misalignment between the seat bottom and back structures can interfere with the proper functioning of inertia sensitive latch mechanisms. Consequently, it is desirable to provide a seat hinge mechanism which is tolerant to seat structure misalignment.
In view of the foregoing, it is a principal object of this invention to provide an improved motor vehicle seat hinge structure having a quandrant component which does not present an objectionable protruding edge surface to rear seat occupants when the front seat is moved forward. It is yet another principal object of this invention to provide an improved seat hinge structure including an inertia sensitive element which is relatively insensitive to misalignment between the seat back and seat bottom structures.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates upon a reading of the described preferred embodiments of this invention taken in conjuction with the accompanying drawings.